Vehicle seats are designed in accordance with ergonomic requirements and in accordance with strict safety requirements defining the strength which must be met by the seat components in case of collision. Seats must be designed such that vehicle occupants with different body dimensions do not suffer from driving fatigue, on the one hand, and on the other hand, in case of collision, suitable protection and body support is provided.
The headrest of a vehicle seat, apart from serving as a head support for comfort and preventing driving fatigue, has an important role in preventing so-called whiplash--type injuries of a person's head in case of collision.
It is accordingly important that the headrest be adjustable in height, so as to meet the specific personal body dimensions of a vehicle's occupant and that in case of sudden impact the head rest does not spontaneously change its position.
Heretofore, a variety of mechanisms have been provided for adjusting the height of a headrest support of a vehicle's seat.
One way of controlling vertical adjustment is by providing some friction means between the headrest support rods and a housing member mounted within a back rest portion of the vehicle's seat. However, a serious drawback of such mechanisms is that friction conditions may change and accordingly positioning of the headrest may unintentionally be changed.
Other means for vertically adjusting a headrest are disclosed, for example, in U.S. Pat. No. 5,156,440, wherein the support rod comprises a plurality of V-shaped notches engageable by a wire spring. However, the disclosure according to this patent provides vertical displacement of the headrest, in both directions (i.e. upwards and downwards) by applying sufficient force in a vertical direction by the occupant. According to this Patent there are no means for unequivocal restraining the head rest at least in a downward direction, and accordingly there are no provisions of any manually operated release means for selectively adjusting the head rest. The drawback involved with such an arrangement is that in case of collision, the headrest may unintentionally change its vertical position in a downward direction, possibly causing severe injury by failing to support an occupants head.
It is the object of the present invention to provide a new and improved headrest support mechanism for adjusting the vertical position of a headrest of a vehicle seat.